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如上文所說，建立了NetConnection，就可以建立NetStream了。在ngx_rtmp是如何實現的呢？

CMD模塊回調注冊

nginx在初始化啟動的時候調用ngx_rtmp_cmd_module模塊ngx_rtmp_cmd_postconfiguration()中進行回調注冊，具體回調如下：

static ngx_rtmp_amf_handler_t ngx_rtmp_cmd_map[] = {
   { ngx_string("connect"),            ngx_rtmp_cmd_connect_init        },
   { ngx_string("createStream"),       ngx_rtmp_cmd_create_stream_init  },
   { ngx_string("closeStream"),        ngx_rtmp_cmd_close_stream_init   },
   { ngx_string("deleteStream"),       ngx_rtmp_cmd_delete_stream_init  },
   { ngx_string("publish"),            ngx_rtmp_cmd_publish_init        },
   { ngx_string("play"),               ngx_rtmp_cmd_play_init           },
   { ngx_string("play2"),              ngx_rtmp_cmd_play2_init          },
   { ngx_string("seek"),               ngx_rtmp_cmd_seek_init           },
   { ngx_string("pause"),              ngx_rtmp_cmd_pause_init          },
   { ngx_string("pauseraw"),           ngx_rtmp_cmd_pause_init          },
};

create stream流程

createStream大體流程如下：

• 如本人的前文《RTMP的connection協議》中所講，客戶端收到客戶端回復的"connect"回應消息后，給服務器發送createstream消息
• 服務端通過ngx_rtmp_recv收到消息后進行組包、頭解析后調用ngx_rtmp_receive_message
• ngx_rtmp_receive_message根據上一步解析出來的消息頭帶的type定位到回調函數ngx_rtmp_cmd_create_stream_init
  而ngx_rtmp_cmd_create_stream_init主要做的工作如下：
• 具體回調是就是從緩沖區中讀取數據ngx_rtmp_receive_amf()
  -調用ngx_rtmp_cmd_create_stream()
• ngx_rtmp_cmd_create_stream()功能相對簡單，就是回復消息給客戶端，amf消息如下：
  static ngx_rtmp_amf_elt_t out_elts[] = {
  { NGX_RTMP_AMF_STRING,
  ngx_null_string,
  "_result", 0 },
  { NGX_RTMP_AMF_NUMBER,
  ngx_null_string,
  &trans, 0 },
  { NGX_RTMP_AMF_NULL,
  ngx_null_string,
  NULL, 0 },
  { NGX_RTMP_AMF_NUMBER,
  ngx_null_string,
  &stream, sizeof(stream) },
  };

Stream狀態

對于創建的stream,存在各個狀態，用于服務端和客戶端進行應對，具體如下，如何應對后文在詳講。

• "NetStream.Play.Reset" --- 播放列表重置
• "NetStream.Play.Start" --- 播放開始
• "NetStream.Buffer.Empty" --- 視頻正在緩沖
• "NetStream.Buffer.Full" --- 緩沖區已填滿
• "NetStream.Play.StreamNotFound" --- 找不到此視頻
• "NetStream.Play.Stop" --- 視頻播放完成
• "NetStream.Pause.Notify" --- 流已暫停
• "NetStream.Unpause.Notify" --- 流已恢復
• "NetStream.Seek.Failed" --- 搜尋失敗
• "NetStream.SeekStart.Notify" --- 搜尋開始
• "NetStream.Seek.Notify" --- 正在搜尋
• "NetStream.Seek.Complete" --- 搜尋完畢
• "NetStream.Publish.Start" --- 發布開始
• "NetStream.Unpublish.Success" --- 停止發布
• "NetStream.Record.Start" --- 開始錄制
• "NetStream.Record.Stop" --- 停止錄制
• "NetStream.Publish.BadName" --- 警告！試圖發布已經被他人發布的流
• "NetStream.Play.PublishNotify" --- 發布開始，信息已經發送到所有訂閱者
• "NetStream.Play.UnpublishNotify" --- 發布停止，信息已經發送到所有訂閱者
• "NetStream.Play.InsufficientBW" --- 警告！客戶端沒有足夠的帶寬，無法以正常速度播放數據"